The Analytical Cytometry Shared Resource (ACSR) is a 400 square foot state-of-the-art facility located in the Comprehensive Cancer Center that is at the center of the University Medical Center complex. The P2 laboratory that holds the cytometry equipment used by CCC members is equipped with a biohazard cell culture hood, centrifuge, water baths, and a fluorescent microscope. The instrumentation within the Shared Resource includes two Coulter EPICS Elite flow cytometer/cell sorters. One of the Elite cell sorters is equipped with a 5 W argon water-cooled laser, a 15 mW air-cooled argon laser and an air-cooled helium-neon laser with upgrades including a 5th photomultiplier tube and a gated amplifier, which provides the capability of performing up to 5 color multiparameter analysis of biological particles. In addition, this instrument has a high- speed "ESP" sort module upgrade which allows high speed sterile sorting of large quantities of cells with high purity and recovery. This instrument can also be used with a modular 96-well format "autoclone" device that can be used to clone and culture single cells from heterogeneous populations. The other Elite cell sorter is equipped with an air-cooled argon laser and a helium-neon laser that is used for analysis of up to 4 parameters and for cell sorting. The facility has recently acquired a Coulter XL-MCL, which is an automated flow cytometer that provides rapid analytical capabilities with more efficient use of technical support. CCC members using the ACSR have access to on-line and off-line computer analysis capabilities, including multiple software programs for analysis of such types of data as DNA content, the presence and abundance of cell cycle proteins, cell populations, undergoing apoptosis, and identification of subpopulations of peripheral blood leukocytes using multiple antibody markers. In addition to the analytical cytometry/cell sorter instrumentation, this laboratory includes a computer-based image analysis system and an off-line computer workstation. Fredika Robertson, Ph.D., is Director of the CC Analytical Cytometry Shared Resource, Andrew Oberysyzn, M.S., is the Senior Research Associate and Key Operator of the cell sorters and Jaime Miracle is the Research Assistant who provides technical support for the automated analyzer. These individuals provide consultation to CCC members for flow cytometry/cell sorting, develop protocols, and provide assistance with data analysis, meeting presentations, and publication quality flow cytometry graphics.